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ISL6443IRZ-T Datasheet(PDF) 10 Page - Intersil Corporation |
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ISL6443IRZ-T Datasheet(HTML) 10 Page - Intersil Corporation |
10 / 18 page 10 FN9044.1 October 4, 2005 Pin Descriptions BOOT2, BOOT1 - These pins power the upper MOSFET drivers of each PWM converter. Connect this pin to the junction of the bootstrap capacitor and the cathode of the bootstrap diode. The anode of the bootstrap diode is connected to the VCC_5V pin. UGATE2, UGATE1 - These pins provide the gate drive for the upper MOSFETs. PHASE2, PHASE1 - These pins are connected to the junction of the upper MOSFETs source, output filter inductor and lower MOSFETs drain. LGATE2, LGATE1 - These pins provide the gate drive for the lower MOSFETs. PGND - This pin provides the power ground connection for the lower gate drivers for both PWM1 and PWM2. This pin should be connected to the sources of the lower MOSFETs and the (-) terminals of the external input capacitors. FB3, FB2, FB1 - These pins are connected to the feedback resistor divider and provide the voltage feedback signals for the respective controller. They set the output voltage of the converter. In addition, the PGOOD circuit uses these inputs to monitor the output voltage status. ISEN2, ISEN1 - These pins are used to monitor the voltage drop across the lower MOSFET for current loop feedback and overcurrent protection. PGOOD - This is an open drain logic output used to indicate the status of the output voltages. This pin is pulled low when either of the two PWM outputs is not within 10% of the respective nominal voltage, or if the linear controller output is less than 75% of it’s nominal value. SGND - (Pin 20 on the TSSOP; Pin 17 on the QFN) This is the small-signal ground, common to all 3 controllers, and must be routed separately from the high current ground (PGND). All voltage levels are measured with respect to this pin. Connect the additional SGND pins to this pin. If using a 5V supply, connect this pin to VCC_5V. A small ceramic capacitor should be connected right next to this pin for noise decoupling. VIN - Use this pin to power the device with an external supply voltage with a range of 5.6V to 24V. For 5V ±10% operation, connect this pin to VCC_5V. VCC_5V - This pin is the output of the internal 5V linear regulator. This output supplies the bias for the IC, the low side gate drivers, and the external boot circuitry for the high side gate drivers. The IC may be powered directly from a single 5V (±10%) supply at this pin. When used as a 5V supply input, this pin must be externally connected to VIN. The VCC_5V pin must be always decoupled to power ground with a minimum of 4.7 µF ceramic capacitor, placed very close to the pin. SYNC - This pin may be used to synchronize two or more ISL6443 controllers. This pin requires a 1K resistor to ground if used; connect directly to VCC_5V if not used. SS1, SS2 - These pins provide a soft-start function for their respective PWM controllers. When the chip is enabled, the regulated 5 µA pull-up current source charges the capacitor connected from this pin to ground. The error amplifier reference voltage ramps from 0 to 0.8V while the voltage on the soft-start pin ramps from 0 to 0.8V. SD1, SD2 - These pins provide an enable/disable function for their respective PWM output. The output is enabled when this pin is floating or pulled HIGH, and disabled when the pin is pulled LOW. GATE3 - This pin is the open drain output of the linear regulator controller. OCSET2, OCSET1 - A resistor from this pin to ground sets the overcurrent threshold for the respective PWM. Functional Description General Description The ISL6443 integrates control circuits for two synchronous buck converters and one linear controller. The two synchronous bucks operate out of phase to substantially reduce the input ripple and thus reduce the input filter requirements. The chip has four control lines (SS1, SD1, SS2, and SD2), which provide independent control for each of the synchronous buck outputs. The buck PWM controllers employ a free-running frequency of 300kHz. The current mode control scheme with an input voltage feed-forward ramp input to the modulator provides excellent rejection of input voltage variations and provides simplified loop compensations. The linear controller can drive either a PNP or PFET to provide ultra low-dropout regulation with programmable voltages. Internal 5V Linear Regulator (VCC_5V) All ISL6443 functions are internally powered from an on- chip, low dropout 5V regulator. The maximum regulator input voltage is 24V. Bypass the regulator’s output (VCC_5V) with a 4.7µF capacitor to ground. The dropout voltage for this LDO is typically 600mV, so when VCC_5V is greater then 5.6V, VCC_5V is typically 5V. The ISL6443 also employs an undervoltage lockout circuit that disables both regulators when VCC_5V falls below 4.4V. The internal LDO can source over 60mA to supply the IC, power the low side gate drivers, charge the external boot capacitor and supply small external loads. When driving large FETs especially at 300kHz frequency, little or no regulator current may be available for external loads. ISL6443 |
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